metal-organic compounds
Tetraammonium μ-ethylenediaminetetraacetato-1κ3O,N,O′:2κ3O′′,N′,O′′′-bis[trioxidotungstate(VI)] tetrahydrate
aLaboratoire de Chimie Minérale et Analytique (LACHIMIA), Département de Chimie, Faculté des Sciences et Techniques, Université Cheikh Anta Diop, Dakar, Senegal
*Correspondence e-mail: lamine.yaffa@ucad.edu.sn
The title compound, (NH4)4[W2(C10H12N2O8)O6]·4H2O, was obtained from a mixture of tungstic acid, ammonia and ethylenediaminetetraacetic acid (H4edta) in a 2:4:1 ratio. The anion of the complex contains two WO3 units and one bridging edta4− ligand. Each central metal atom is tridentately coordinated by nitrogen and two carboxylate groups of the edta4− ligand, together with the three oxido ligands, producing a distorted octahedral coordination environment around each tungsten atom. The center of the carbon–carbon bond of the ethylene bridge represents a crystallographic inversion center. The consists of a three-dimensional supramolecular framework built up by the dinuclear cations, the ammonium counter-ions and the solvent water molecules via hydrogen bonds of the N—H⋯O and O—H⋯O type.
CCDC reference: 2112632
Structure description
Research on inorganic–organic framework materials is one of the fastest growing areas in materials chemistry because of their unique hybrid nature, which enables the combination of properties from both inorganic and organic materials (Cheetham & Rao, 2007). As organic ligands, polycarboxylates are multidentate chelating agents that are widespread in nature and industry because of their ability to coordinate with various transition metals in different ratios (Nicolau & Guy, 1995; Langer, 2000).
As a part of this field, molybdenum polycarboxylate complexes have thus been thoroughly investigated over the past three decades (Lee & Holm, 2004). Some well-characterized mono-, bi- and polynuclear molybdenum and tungsten complexes have been reported, for example Mo2(O2CCH2OH)4, M2[MoO3(C2O4)] (M = Na, K, Rb, Cs), Na2[MO2(C6H6O7)2]·3H2O (M = Mo, W) (Cotton et al., 2002; Cindríc et al., 2000; Zhou et al., 1999). Structural analyses of WVI–edta complexes are rare in the literature. Together with the structure of Na2K2[Mo2O6(edta)]·10H2O, the structure of Na4[W2O6(edta)]·8H2O has been published (Lin et al., 2006).
Nevertheless, tungsten has been reported to incorporate into several enzymes (Johnson et al., 1996). In fact, tungsten could be a useful probe for the active site of molybdenum enzymes. As a consequence, more effort has been put into tungsten chemistry by inorganic and bioinorganic chemists (Bagno & Bonchio, 2000; Enemark et al., 2004; Sung & Holm, 2001; Zhou et al., 2004).
In this study, the reaction of H4edta with tungstic acid has been investigated and a new binuclear 2:1 W–edta complex, (NH4)4[W2(C10H12N2O8)O6]·4H2O, was isolated and structurally characterized.
As shown in Fig. 1, the dinuclear anion of the title compound shows one edta4− ligand bonded to two tungstate WO3 units. Each W atom is six-coordinate in a distorted octahedral environment built up by the tridentate facial coordination of one N and two O atoms of the edta4− ligand as well as by three oxido ligands. The edta4− ligand itself therefore acts as a bridge between the two WO3 units, with the central carbon–carbon bond also representing a crystallographic center of inversion. The anion is accompanied by four ammonium cations and four solvent water molecules.
The three terminal oxido ligands bonded to the metal, i.e. W=Ot (Ot = O3, O6, O8) show bond lengths in a range 1.753 (2) to 1.759 (2) Å. The resulting Ot—W—Ot bond angles [105.05 (9), 105.14 (9), 103.12 (10)°] are considerably larger than 90° expected for a regular octahedron. Bond distances of the oxygen atoms of edta4− to W are 2.135 (2) and 2.159 (2) Å, respectively and therefore significantly longer than the W=Ot bonds.
In the ). Two neighboring complexes are connected via hydrogen bonds of the N—H⋯Ow—H⋯O, N—H⋯O and Ow—H⋯O types. These interactions lead to the supramolacular structure shown in Fig. 2.
the complex anion, ammonium cations and solvent water molecules interact through medium–strong classical hydrogen bonds (Table 1Synthesis and crystallization
Tungstic acid (4 mmol, 0.999 g) and ammonia solution (8 mmol, 1.001 g) were mixed in 30 ml of water to solubilize the WVI source. To this mixture was slowly added ethylenediammine-tetraacetic acid (H4edta) (2 mmol, 0.584 g) under vigorous stirring. The solution was then stirred for two h at room temperature. The colorless solution thus obtained was left at room temperature for slow evaporation of water. After two weeks, colorless crystals (yield 11.6% based on W) were obtained from the solution.
The FT–infrared spectra of the title compound shows well-resolved absorption bands for the carboxylate of the coordinating edta4− at 1651 cm−1 and 1402 cm−1, which are attributed to the antisymmetric and symmetric stretching vibrations ν(COO–). The bands at 926, 857 and 666 cm−1 can be attributed to symmetric and asymmetric W=Ot stretching vibrations (Lin et al., 2006; Li et al., 2007). The range of 3500–2800 cm−1 shows many bands ascribed to O—H stretching of water molecules, as well as N—H stretching vibrations of ammonium cations (Yaffa et al., 2020).
Refinement
Crystal data, data collection and structure .
details are summarized in Table 2
|
Structural data
CCDC reference: 2112632
https://doi.org/10.1107/S2414314621009822/im4013sup1.cif
contains datablock I. DOI:Structure factors: contains datablock I. DOI: https://doi.org/10.1107/S2414314621009822/im4013Isup2.hkl
Data collection: APEX2 (Bruker, 2016); cell
SAINT (Bruker, 2016); data reduction: SAINT (Bruker, 2016); program(s) used to solve structure: SHELXS (Sheldrick, 2008); program(s) used to refine structure: SHELXL2014/6 (Sheldrick, 2015); molecular graphics: OLEX2 (Dolomanov et al., 2009); software used to prepare material for publication: OLEX2 (Dolomanov et al., 2009).(NH4)4[W2(C10H12N2O8)O6]·4H2O | F(000) = 860 |
Mr = 896.15 | Dx = 2.374 Mg m−3 |
Monoclinic, P21/c | Mo Kα radiation, λ = 0.71073 Å |
a = 6.8017 (5) Å | Cell parameters from 9817 reflections |
b = 7.7194 (5) Å | θ = 2.8–27.6° |
c = 23.9807 (19) Å | µ = 9.26 mm−1 |
β = 95.345 (3)° | T = 150 K |
V = 1253.63 (16) Å3 | Block, colourless |
Z = 2 | 0.18 × 0.18 × 0.14 mm |
Bruker APEXII CCD diffractometer | 2703 reflections with I > 2σ(I) |
φ and ω scans | Rint = 0.053 |
Absorption correction: multi-scan (SADABS; Bruker, 2016) | θmax = 27.6°, θmin = 2.8° |
Tmin = 0.444, Tmax = 0.746 | h = −8→8 |
55419 measured reflections | k = −10→10 |
2890 independent reflections | l = −31→31 |
Refinement on F2 | Primary atom site location: structure-invariant direct methods |
Least-squares matrix: full | Hydrogen site location: mixed |
R[F2 > 2σ(F2)] = 0.014 | H atoms treated by a mixture of independent and constrained refinement |
wR(F2) = 0.034 | w = 1/[σ2(Fo2) + (0.0138P)2 + 1.4846P] where P = (Fo2 + 2Fc2)/3 |
S = 1.07 | (Δ/σ)max = 0.002 |
2890 reflections | Δρmax = 0.71 e Å−3 |
201 parameters | Δρmin = −0.85 e Å−3 |
0 restraints |
Geometry. All esds (except the esd in the dihedral angle between two l.s. planes) are estimated using the full covariance matrix. The cell esds are taken into account individually in the estimation of esds in distances, angles and torsion angles; correlations between esds in cell parameters are only used when they are defined by crystal symmetry. An approximate (isotropic) treatment of cell esds is used for estimating esds involving l.s. planes. |
Refinement. All non-hydrogen atoms were refined anisotropically. Hydrogen atoms bonded to carbon and oxygen were placed in idealized positions and refined using a riding model with isotropic displacement parameters calculated as Uiso(H) = 1.2Ueq(C) for ethylene and methylene hydrogen atoms and Uiso(H) = 1.5Ueq(O) for solvent water molecules. Hydrogen atoms of the ammonium cations were located in the difference-Fourier map and refined isotropically. |
x | y | z | Uiso*/Ueq | ||
W1 | 0.40177 (2) | 0.69956 (2) | 0.10889 (2) | 0.01546 (4) | |
O6 | 0.4717 (3) | 0.7513 (3) | 0.04235 (8) | 0.0290 (4) | |
O3 | 0.5793 (3) | 0.7989 (2) | 0.15614 (9) | 0.0270 (4) | |
O9 | 0.2095 (3) | 0.6721 (2) | 0.17381 (8) | 0.0237 (4) | |
N4 | 0.0791 (3) | 0.6278 (2) | 0.06743 (8) | 0.0143 (4) | |
O8 | 0.4519 (3) | 0.4764 (2) | 0.11461 (8) | 0.0276 (4) | |
O5 | −0.0230 (3) | 0.5116 (3) | 0.20717 (8) | 0.0351 (5) | |
C7 | −0.0056 (4) | 0.5133 (3) | 0.10897 (10) | 0.0192 (5) | |
H7A | 0.0366 | 0.3924 | 0.1033 | 0.023* | |
H7B | −0.1515 | 0.5173 | 0.1031 | 0.023* | |
C11 | 0.0609 (4) | 0.5690 (3) | 0.16809 (11) | 0.0200 (5) | |
C12 | 0.0980 (4) | 0.5353 (3) | 0.01373 (11) | 0.0190 (5) | |
H12A | 0.1915 | 0.4378 | 0.0208 | 0.023* | |
H12B | 0.1546 | 0.6157 | −0.0127 | 0.023* | |
O7 | −0.0275 (3) | 1.0904 (2) | 0.07169 (9) | 0.0280 (4) | |
O4 | 0.2366 (3) | 0.9388 (2) | 0.10315 (9) | 0.0253 (4) | |
C1 | 0.0597 (4) | 0.9519 (3) | 0.07921 (11) | 0.0183 (5) | |
C8 | −0.0402 (4) | 0.7886 (3) | 0.05795 (12) | 0.0219 (5) | |
H8A | −0.1639 | 0.7748 | 0.0762 | 0.026* | |
H8B | −0.0769 | 0.8012 | 0.0172 | 0.026* | |
N10 | 0.4415 (4) | 0.8304 (3) | −0.06894 (11) | 0.0225 (5) | |
O2 | 0.7912 (3) | 1.0837 (3) | 0.19478 (9) | 0.0357 (5) | |
H2A | 0.7148 | 0.9966 | 0.1847 | 0.054* | |
H2B | 0.8584 | 1.0492 | 0.2254 | 0.054* | |
O1 | 0.2481 (3) | 1.1729 (3) | 0.19796 (10) | 0.0367 (5) | |
H1A | 0.2243 | 1.1196 | 0.1661 | 0.055* | |
H1B | 0.1322 | 1.2036 | 0.2070 | 0.055* | |
N11 | 0.5898 (4) | 0.3808 (4) | 0.23069 (12) | 0.0262 (5) | |
H10A | 0.456 (5) | 0.808 (4) | −0.0300 (16) | 0.032 (9)* | |
H10B | 0.521 (5) | 0.904 (5) | −0.0757 (14) | 0.034 (9)* | |
H10C | 0.316 (6) | 0.864 (5) | −0.0785 (16) | 0.045 (10)* | |
H10D | 0.471 (6) | 0.735 (5) | −0.0853 (17) | 0.046 (11)* | |
H11A | 0.515 (6) | 0.409 (6) | 0.2004 (19) | 0.060 (13)* | |
H11B | 0.517 (7) | 0.355 (6) | 0.256 (2) | 0.069 (14)* | |
H11C | 0.662 (6) | 0.466 (6) | 0.2389 (17) | 0.054 (12)* | |
H11D | 0.663 (6) | 0.288 (5) | 0.2208 (17) | 0.047 (11)* |
U11 | U22 | U33 | U12 | U13 | U23 | |
W1 | 0.01185 (5) | 0.01695 (6) | 0.01687 (6) | −0.00047 (3) | −0.00242 (4) | 0.00027 (4) |
O6 | 0.0201 (10) | 0.0457 (11) | 0.0211 (10) | −0.0102 (9) | 0.0011 (8) | 0.0012 (9) |
O3 | 0.0216 (10) | 0.0330 (11) | 0.0253 (10) | −0.0030 (8) | −0.0044 (8) | −0.0031 (8) |
O9 | 0.0244 (10) | 0.0285 (10) | 0.0182 (9) | −0.0082 (8) | 0.0019 (8) | −0.0016 (7) |
N4 | 0.0136 (9) | 0.0125 (9) | 0.0161 (10) | −0.0008 (7) | −0.0026 (8) | 0.0005 (8) |
O8 | 0.0255 (10) | 0.0208 (9) | 0.0344 (11) | 0.0069 (8) | −0.0087 (8) | −0.0021 (8) |
O5 | 0.0297 (11) | 0.0522 (13) | 0.0233 (10) | −0.0139 (10) | 0.0015 (8) | 0.0115 (10) |
C7 | 0.0173 (12) | 0.0174 (12) | 0.0225 (13) | −0.0051 (9) | −0.0006 (10) | 0.0026 (10) |
C11 | 0.0174 (12) | 0.0193 (12) | 0.0227 (13) | 0.0011 (9) | −0.0011 (10) | 0.0044 (10) |
C12 | 0.0165 (12) | 0.0215 (12) | 0.0186 (12) | −0.0022 (9) | −0.0010 (10) | −0.0051 (10) |
O7 | 0.0256 (10) | 0.0166 (9) | 0.0411 (12) | 0.0055 (8) | −0.0012 (8) | 0.0011 (8) |
O4 | 0.0190 (9) | 0.0153 (9) | 0.0396 (12) | −0.0016 (7) | −0.0083 (8) | −0.0005 (8) |
C1 | 0.0169 (12) | 0.0176 (12) | 0.0202 (13) | 0.0004 (9) | 0.0013 (9) | 0.0015 (9) |
C8 | 0.0177 (12) | 0.0142 (12) | 0.0320 (15) | 0.0019 (9) | −0.0070 (11) | 0.0018 (10) |
N10 | 0.0215 (12) | 0.0178 (11) | 0.0279 (14) | −0.0025 (9) | 0.0010 (10) | 0.0034 (10) |
O2 | 0.0462 (13) | 0.0282 (11) | 0.0316 (12) | −0.0025 (10) | −0.0022 (10) | −0.0008 (9) |
O1 | 0.0333 (12) | 0.0386 (12) | 0.0377 (13) | −0.0046 (10) | 0.0013 (10) | −0.0024 (10) |
N11 | 0.0272 (13) | 0.0256 (13) | 0.0254 (13) | −0.0032 (11) | 0.0000 (11) | 0.0033 (11) |
W1—O6 | 1.7529 (19) | O7—C1 | 1.228 (3) |
W1—O3 | 1.7534 (19) | O4—C1 | 1.288 (3) |
W1—O9 | 2.1350 (19) | C1—C8 | 1.499 (3) |
W1—N4 | 2.3884 (19) | C8—H8A | 0.9900 |
W1—O8 | 1.7590 (19) | C8—H8B | 0.9900 |
W1—O4 | 2.1590 (17) | N10—H10A | 0.95 (4) |
O9—C11 | 1.284 (3) | N10—H10B | 0.81 (4) |
N4—C7 | 1.487 (3) | N10—H10C | 0.90 (4) |
N4—C12 | 1.488 (3) | N10—H10D | 0.87 (4) |
N4—C8 | 1.489 (3) | O2—H2A | 0.8701 |
O5—C11 | 1.225 (3) | O2—H2B | 0.8698 |
C7—H7A | 0.9900 | O1—H1A | 0.8701 |
C7—H7B | 0.9900 | O1—H1B | 0.8698 |
C7—C11 | 1.510 (4) | N11—H11A | 0.87 (5) |
C12—C12i | 1.531 (5) | N11—H11B | 0.84 (5) |
C12—H12A | 0.9900 | N11—H11C | 0.83 (4) |
C12—H12B | 0.9900 | N11—H11D | 0.92 (4) |
O6—W1—O3 | 105.05 (9) | N4—C12—C12i | 113.7 (3) |
O6—W1—O9 | 157.36 (9) | N4—C12—H12A | 108.8 |
O6—W1—N4 | 89.46 (8) | N4—C12—H12B | 108.8 |
O6—W1—O8 | 103.12 (10) | C12i—C12—H12A | 108.8 |
O6—W1—O4 | 86.03 (9) | C12i—C12—H12B | 108.8 |
O3—W1—O9 | 90.22 (8) | H12A—C12—H12B | 107.7 |
O3—W1—N4 | 157.08 (8) | C1—O4—W1 | 123.67 (15) |
O3—W1—O8 | 105.14 (9) | O7—C1—O4 | 123.5 (2) |
O3—W1—O4 | 89.42 (8) | O7—C1—C8 | 119.0 (2) |
O9—W1—N4 | 71.28 (7) | O4—C1—C8 | 117.4 (2) |
O9—W1—O4 | 77.36 (8) | N4—C8—C1 | 115.2 (2) |
O8—W1—O9 | 88.46 (8) | N4—C8—H8A | 108.5 |
O8—W1—N4 | 88.23 (8) | N4—C8—H8B | 108.5 |
O8—W1—O4 | 159.79 (8) | C1—C8—H8A | 108.5 |
O4—W1—N4 | 73.71 (7) | C1—C8—H8B | 108.5 |
C11—O9—W1 | 120.89 (17) | H8A—C8—H8B | 107.5 |
C7—N4—W1 | 104.91 (14) | H10A—N10—H10B | 108 (3) |
C7—N4—C12 | 111.36 (19) | H10A—N10—H10C | 108 (3) |
C7—N4—C8 | 110.97 (19) | H10A—N10—H10D | 106 (3) |
C12—N4—W1 | 108.76 (14) | H10B—N10—H10C | 112 (3) |
C12—N4—C8 | 110.94 (19) | H10B—N10—H10D | 108 (4) |
C8—N4—W1 | 109.70 (14) | H10C—N10—H10D | 113 (4) |
N4—C7—H7A | 109.4 | H2A—O2—H2B | 104.5 |
N4—C7—H7B | 109.4 | H1A—O1—H1B | 104.5 |
N4—C7—C11 | 111.03 (19) | H11A—N11—H11B | 109 (4) |
H7A—C7—H7B | 108.0 | H11A—N11—H11C | 106 (4) |
C11—C7—H7A | 109.4 | H11A—N11—H11D | 106 (4) |
C11—C7—H7B | 109.4 | H11B—N11—H11C | 113 (4) |
O9—C11—C7 | 116.1 (2) | H11B—N11—H11D | 112 (4) |
O5—C11—O9 | 124.1 (3) | H11C—N11—H11D | 111 (4) |
O5—C11—C7 | 119.7 (2) | ||
W1—O9—C11—O5 | 159.8 (2) | C7—N4—C12—C12i | 58.5 (3) |
W1—O9—C11—C7 | −18.0 (3) | C7—N4—C8—C1 | 111.6 (2) |
W1—N4—C7—C11 | 35.7 (2) | C12—N4—C7—C11 | 153.2 (2) |
W1—N4—C12—C12i | 173.6 (2) | C12—N4—C8—C1 | −124.0 (2) |
W1—N4—C8—C1 | −3.8 (3) | O7—C1—C8—N4 | 178.2 (2) |
W1—O4—C1—O7 | −173.4 (2) | O4—C1—C8—N4 | 0.2 (4) |
W1—O4—C1—C8 | 4.4 (3) | C8—N4—C7—C11 | −82.7 (2) |
N4—C7—C11—O9 | −16.0 (3) | C8—N4—C12—C12i | −65.6 (3) |
N4—C7—C11—O5 | 166.0 (2) |
Symmetry code: (i) −x, −y+1, −z. |
D—H···A | D—H | H···A | D···A | D—H···A |
C7—H7A···O7ii | 0.99 | 2.48 | 3.384 (3) | 152 |
C12—H12B···O7iii | 0.99 | 2.77 | 3.548 (3) | 136 |
C8—H8A···O6iv | 0.99 | 2.54 | 3.319 (3) | 135 |
C8—H8B···O7iii | 0.99 | 2.46 | 3.319 (4) | 145 |
O2—H2A···O3 | 0.87 | 1.88 | 2.743 (3) | 171 |
O2—H2B···O5v | 0.87 | 1.90 | 2.763 (3) | 170 |
O1—H1A···O7 | 0.87 | 2.72 | 3.468 (3) | 145 |
O1—H1A···O4 | 0.87 | 2.06 | 2.900 (3) | 161 |
O1—H1B···O2iv | 0.87 | 2.49 | 3.177 (3) | 137 |
N10—H10A···O6 | 0.95 (4) | 1.78 (4) | 2.727 (3) | 175 (3) |
N10—H10B···O4vi | 0.81 (4) | 2.20 (4) | 2.996 (3) | 168 (3) |
N10—H10C···O7iii | 0.90 (4) | 2.01 (4) | 2.876 (3) | 160 (3) |
N10—H10D···O8vii | 0.87 (4) | 1.87 (4) | 2.736 (3) | 175 (4) |
N11—H11A···O8 | 0.87 (5) | 2.13 (5) | 2.947 (3) | 156 (4) |
N11—H11B···O3viii | 0.84 (5) | 2.31 (5) | 3.109 (3) | 160 (4) |
N11—H11C···O1viii | 0.83 (4) | 2.25 (4) | 2.979 (4) | 147 (4) |
N11—H11D···O2ii | 0.92 (4) | 1.93 (4) | 2.846 (4) | 173 (4) |
Symmetry codes: (ii) x, y−1, z; (iii) −x, −y+2, −z; (iv) x−1, y, z; (v) −x+1, y+1/2, −z+1/2; (vi) −x+1, −y+2, −z; (vii) −x+1, −y+1, −z; (viii) −x+1, y−1/2, −z+1/2. |
Acknowledgements
The authors acknowledge the Cheikh Anta Diop University of Dakar (Senegal), the Institute of Inorganic Chemistry I, Ulm University and the Helmholtz Institute Ulm (HIU) for Electrochemical Energy Storage, Albert-Einstein-Allee 11, 89081 Ulm, Germany, for financial support and instrumentation use.
References
Bagno, A. & Bonchio, M. (2000). Chem. Phys. Lett. 317, 123–128. CrossRef CAS Google Scholar
Bruker (2016). Bruker (2016). APEX2, SAINT and SADABS. Bruker AXS Inc., Madison, Wisconsin, USA. Google Scholar
Cheetham, A. K. & Rao, C. N. R. (2007). Science, 318, 58–59. Web of Science CrossRef PubMed CAS Google Scholar
Cindrić, M., Strukan, N., Vrdoljak, V., Devčić, M., Veksli, Z. & Kamenar, B. (2000). Inorg. Chim. Acta, 304, 260–267. Web of Science CSD CrossRef CAS Google Scholar
Cotton, F. A., Barnard, T. S., Daniels, L. M. & Murillo, C. A. (2002). Inorg. Chem. Commun. 5, 527–532. Web of Science CSD CrossRef CAS Google Scholar
Dolomanov, O. V., Bourhis, L. J., Gildea, R. J., Howard, J. A. K. & Puschmann, H. (2009). J. Appl. Cryst. 42, 339–341. Web of Science CrossRef CAS IUCr Journals Google Scholar
Enemark, J. H., Cooney, J. J. A., Wang, J. J. & Holm, R. H. (2004). Chem. Rev. 104, 1175–1200. CrossRef PubMed CAS Google Scholar
Johnson, M. K., Rees, D. C. & Adams, M. W. W. (1996). Chem. Rev. 96, 2817–2840. CrossRef PubMed CAS Google Scholar
Langer, R. (2000). Acc. Chem. Res. 33, 94–101. CrossRef PubMed CAS Google Scholar
Lee, S. C. & Holm, R. H. (2004). Chem. Rev. 104, 1135–1158. CrossRef PubMed CAS Google Scholar
Li, D.-M., Cui, L.-F., Xing, Y.-H., Xu, J.-Q., Yu, J.-H., Wang, T., Jia, H. & Hu, N. (2007). J. Mol. Struct. 832, 138–145. CSD CrossRef CAS Google Scholar
Lin, H. B., Chen, C. Y., Liao, X. L., Lin, T. R. & Zhou, Z. H. (2006). Synth. React. Inorg. Met.-Org. Nano-Met. Chem. 36, 411–414. CSD CrossRef CAS Google Scholar
Nicolaou, K. C. & Guy, R. K. (1995). Angew. Chem. Int. Ed. Engl. 34, 2079–2090. CrossRef CAS Google Scholar
Sheldrick, G. M. (2008). Acta Cryst. A64, 112–122. Web of Science CrossRef CAS IUCr Journals Google Scholar
Sheldrick, G. M. (2015). Acta Cryst. C71, 3–8. Web of Science CrossRef IUCr Journals Google Scholar
Sung, K. M. & Holm, R. H. (2001). Inorg. Chem. 40, 4518–4525. CSD CrossRef PubMed CAS Google Scholar
Yaffa, L., Kama, A. B., Sall, M. L., Diop, C. A. K., Sidibé, M., Giorgi, M., Diop, M. & Gautier, R. (2020). Polyhedron, 191, 1–6. CSD CrossRef Google Scholar
Zhou, Z.-H., Hou, S. Y., Cao, Z.-X., Wan, H. L. & Ng, S. W. (2004). J. Inorg. Biochem. 98, 1037–1044. CSD CrossRef PubMed CAS Google Scholar
Zhou, Z. H., Wan, H. L. & Tsai, K. R. (1999). J. Chem. Soc. Dalton Trans. pp. 4289–4290. CSD CrossRef Google Scholar
This is an open-access article distributed under the terms of the Creative Commons Attribution (CC-BY) Licence, which permits unrestricted use, distribution, and reproduction in any medium, provided the original authors and source are cited.